Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-09-22
2001-09-18
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S075000, C701S092000, C303S122050
Reexamination Certificate
active
06292733
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to vehicular brake controlling apparatus in which a braking liquid pressure for rear road wheels is executed to prevent a lock of the rear road wheel(s) earlier than front road wheel(s) during a braking operation of the vehicle.
b) Description of the Related Art
Since a wheel load of each front road wheel(s) is Increased whereas that of each rear road wheel(s) is decreased during a vehicular braking, there is a strong tendency of the rear road wheel(s) as compared with the case of the front road wheel(s). Hence, if the rear road wheel(s) should be locked at an earlier time than the front road wheel(s), a vehicular behavior would become unstable.
In order to equalize the lock tendencies between the rear and front road wheels, it is known that the braking force is acted upon the front and rear road wheels in accordance with an ideal braking force distribution. Hence, in general, a proportioning valve is interposed in a braking conduit to raise the braking liquid pressure for the front and rear road wheels on the basis of the ideal braking force distribution.
Recently, various types of vehicular anti-skid (or anti-lock) brake control systems (so-called, ABS) to prevent the vehicular road wheel locks from occurring have been mounted in many automotive vehicles.
A Japanese Patent Application First Publication No. Heisei 5-278585 exemplifies one of the anti-lock brake control systems using a brake unit capable of executing the ABS control to achieve the same function as the proportioning valve. The Japanese Patent Application First Publication identified above teaches a braking force distribution control such that when the revolution velocity of the rear road wheel(s) is slower than that of the front road wheel(s), a rear-road-wheel brake actuator is activated to suppress a boosting of a braking liquid pressure for the rear road wheel(s) such as a pressure decrease or hold of a pressure and, when the revolution velocity of the front road wheel(s) is faster than that of the rear road wheel(s), the rear-road-wheel brake actuator is activated to recover the brake liquid pressure.
On the other hand, the brake controlling apparatus in which the braking force distribution control using the brake unit is executed has been proposed in which a predetermined back-up control is executed when a failure in the brake controlling apparatus occurs. For example, the execution of the braking force distribution control is inhibited during a detection of the failure (refer to a Japanese Patent Application First Publication No. Heisei 6-211116 published on Aug. 2, 1994).
Furthermore, a German Patent Application First Publication No. DE-A1 44 14 980 published on Nov. 2, 1995 exemplifies another previously proposed vehicular brake controlling apparatus in which the braking force distribution control is continued on the basis of any signals derived from vehicular road wheel revolution velocity sensors which function normally when the failure of any one of the road wheel revolution velocity sensors occurs and a left-and-right road wheel synchronous control is advanced when executing the braking force distribution control for the rear road wheels in the case where either of the rear road wheel revolution velocity sensors has failed.
SUMMARY OF THE INVENTION
However, if the failure occurs in any one of the road wheel velocity sensors and the left-and-right-road-wheel synchronous control is executed or the braking force distribution control using the normally functioning road wheel sensors is continued, the following problems occur.
First, in a case where the back-up control executing the left-and-right road wheel synchronous control with one of the rear road wheel revolution velocity sensors failed, the following problems occur when the brake operation is carried out during a turn of the vehicle.
a) A case where the failed road wheel velocity sensor is positioned at an inner wheel with respect to a turning direction.
The road wheel velocity of the inside road wheel with respect to the turning direction becomes lower than that of an outer wheel with respect to the turning direction.
In a case where the braking force distribution of the rear two road wheels in the left-and-right road wheel synchronous control mode are carried out on the basis of the road wheel revolution velocity sensors which is located on one of the rear road wheels which is outside with respect to the turning direction, a controller determines that a more braking force should be applied (an insufficient braking force) to the outside wheel since the wheel load on the outside wheel is large, the revolution velocity is high, and a large braking force can be applied. At this time, since the inside road wheel with respect to the turning direction is also determined to have the insufficient braking force, the incremental pressure control of the braking liquid pressure is carried out.
However, since the wheel load on the road wheel during the turning is lower than the outside road wheel during the turning, the lock tendency of the inner road wheel becomes stronger so that a running stability of the vehicle becomes deteriorated.
b) A case where the failed road wheel revolution velocity sensor is located on the outside road wheel during the turning.
Since, in this case, the road wheel velocity of the outside road wheel during the turning becomes higher than the inner wheel during the turning, the rear two road wheels are synchronously controlled as the left-and-right road wheels on the basis of the normally functioning road wheel velocity sensor on the inside wheel during the turning, the lock tendency of the inside wheel during the braking becomes high since the weight load of the inside wheel is lower and the revolution velocity of the inside wheel is low. If the inside wheel is determined to have an excessive braking force, the outside wheel is also determined to have the excessive braking force, the pressure decrease control of the braking liquid pressure is carried out. Consequently, the insufficient braking liquid pressure of the outside wheel is resulted and the braking distance of the vehicle becomes long.
Next, in a case where the back-up control is advanced in which the braking force distribution control is continued with the road wheel revolution velocities of the front left and right road wheels determined on the basis of a detected value of one of the front left and right road wheel revolution velocity sensors when the other of the front left and right road wheel velocity sensors has failed, the following problem occurs.
Especially, in a case where the failed road wheel velocity sensor is located on the outside wheel, the revolution velocity of the front road wheel is determined on the basis of the road wheel velocity of the inside wheel which is lower than the outside wheel.
The lock-up control of the braking force distribution control is executed on the basis of the difference between the road wheel velocities of the inside wheel of the front left and right road wheels during the turning and of the rear left and right road wheels. At this time, the start threshold value of the rear road wheels is set to a lower value so that a start of the pressure decrease control for the rear road wheels may be delayed. In this case, the lock tendencies of the rear left and right road wheels become strong and the running stability of the vehicle becomes deteriorated.
It is therefore an object of the present invention to provide an improved vehicular brake controlling apparatus which prevents an increase in the lock tendencies of the rear road wheels due to an excessive braking force so as to prevent a deterioration of the vehicular running stability and prevent the increase in the braking distance due to the insufficient braking force even when one of the vehicular road wheel velocity sensors has failed and the back-up control is executed during the turn of the vehicle in which the braking force distribution control is continued on the basis of the detected values of
Kojima Toru
Sugiyama Yoshitaka
Chin Gary
Foley & Lardner
Unisia Jecs Corporation
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